> On Aug 1, 2026, at 3:00 AM, Bill Degnan via cctalk <[email protected]>
> wrote:
>
> I dont' know. I watched as Dave Gesswein ran them through his TU56.
Did he use read-all mode to read the raw tape structure? Or is this something
lower level still, without using a TC11 controller?
> I was
> able to load the pdp8 and pdp11 tape
> images using simH, I have not
> yet tried the pdp10 tape image. The TU56 is a universal drive and as I
> underatand it (barely), and if I understand correctly the tracks of 00's
> are ignored and/or are used to indicate what kind of system made them, 12,
> 16, or 18 bit.
True. I remember a DECtape manua, perhaps the TC11/TU56 technical manual, with
an appendix that shows the PDP-n DECtapes for all n, and the matrix of
interoperabiltiy. So if you have a PDP-4 and needed to read PDP-11 DECtapes,
it would tell you whether that's possible.
DECtapes basically have a clock track, a "mark" track, and 3 data tracks, all
of these replicated. And controllers like the TC11 have a "read-all" mode
where pretty much everything is extracted, I'm having some trouble finding out
the precise details of how that deals with the block delimiters, block numbers,
etc.
The one thing a TC11 can't handle is LINCtape, because its low level encoding
is different. I think the drive can handle it if you capture the waveforms,
it's compatible at that level, but the controller even in read-all mode can't
cope.
paul
